LONDON (Thomson Reuters Foundation) - Targeted efforts to make food systems more efficient in key parts of the world could meet the basic calorie needs of 3 billion extra people and reduce the environmental footprint of agriculture without using additional land and water, researchers said on Thursday.

In a study published in the journal Science, researchers from the University of Minnesota's Institute on the Environment looked at 17 key crops that produce 86 percent of the world's crop calories and account for most irrigation and fertiliser consumption, including rice, wheat and corn.

The biggest opportunities for boosting food production lie in Africa, they suggested, while initiatives to make agriculture more sustainable should focus on six countries - China, India, the United States, Brazil, Indonesia and Pakistan - as well as Europe.

Their main recommendations are to produce more food on existing farmland by increasing yields, reduce greenhouse gas emissions from agriculture, use less nutrients and water to grow crops, feed fewer crops to animals as fodder, and cut food waste.

"Sustainably feeding people today and in the future is one of humanity's grand challenges. Agriculture is the main source of water use, greenhouse gas emissions and habitat loss, yet we need to grow more food," said the study's lead author Paul West, co-director of the Institute on the Environment's Global Landscapes Initiative.

"By focusing on areas, crops and practices with the most to be gained, companies, governments, NGOs and others can ensure that their efforts are being targeted in a way that best accomplishes the common and critically important goal of feeding the world while protecting the environment," he added in a statement.

The U.N. Food and Agriculture Organisation (FAO) says food production needs to rise by 60 percent to feed a projected global population of more than 9.5 billion people by mid-century, up from around 7 billion now.

But global production of food is responsible for more than 70 percent of freshwater consumption and 80 percent of deforestation, while over a fifth of all cultivated land and 30 percent of forests are being degraded by unsustainable agriculture, according to the United Nations Environment Programme (UNEP).

BOOSTING YIELDS, SAVING WATER

The University of Minnesota study found that closing even 50 percent of the agricultural "yield gap" - the difference between potential and actual crop yield - in regions with the widest gaps could provide enough calories to feed 850 million people. Nearly half the potential gains are in Africa, and most of the rest in Asia and eastern Europe, it said.

In terms of the nutrients used to help crops grow, 60 percent of nitrogen and nearly half of phosphorus applications exceed what crops need, the study said. China, India and the United States - and the three crops rice, wheat and corn - are the biggest sources of excess nutrient use worldwide, and so could be targeted for the largest improvements.

When it comes to water, rice and wheat are the crops that create the most demand for irrigation worldwide, while India, Pakistan, China and the United States account for the bulk of irrigation water use in water-limited areas, the study said. Using water more efficiently could reduce demand for it by 8 to 15 percent without compromising food production, it added.

The world could also stop feeding so many crops to animals, as the calories contained in fodder are sufficient to meet the needs of 4 billion people, the researchers found. While cultural preferences for meat eating in Western nations and China make changing this difficult, crops could be shifted from animal feed to human food as a "safety net" when weather or pests create shortages, they proposed.

Wasting less food, particularly animal products, could also make a difference. Reducing food waste in the United States, China and India alone could yield food for more than 400 million people, the report said.

A separate study on food security in India and Uganda, released this week by UNEP and partners, found that promoting crop diversification and new water- and energy-efficient technologies could save millions of hectare-metres (1 ha m = 10,000 cubic metres) of water annually, as well as millions of dollars in energy costs.

According to the research, shifting the dominant cropping pattern in the Indian state of Punjab from rice to a mix of maize, cotton, sugarcane, pulses, fodder, fruits, vegetables and agro-forestry could reduce agricultural water use by 1.58 million hectare-metres a year, for example.

In Uganda, meanwhile, the agricultural sector produces only a quarter to half of potential crop and livestock yields due to poor production methods, despite favourable climatic conditions, said the study, which aims to help policy makers and researchers address the problem of low yields.